IN-VITRO RELATIONSHIPS BETWEEN VERTEBRAL BODY DENSITY, SIZE, AND COMPRESSIVE STRENGTH IN THE ELDERLY THORACOLUMBAR SPINE

The bone density of thoracolumbar vertebral columns (T-1-L(2)) from 12 individuals having a mean age of 73 years was examined using quantita tive computed tomography and dual energy X-ray absorptiometry. Spinal units, comprising three vertebrae, from different regions were then te sted for compressive strength in a materials test device. Results show ed segmental variations in trabecular and integral bone density of the vertebral bodies and their capacity for load bearing. Failure strengt h increased craniocaudally, whereas failure stress (load/cross-section al area) decreased. Vertebral compressive strength was moderately corr elated with bone mineral density as assessed with dual energy X-ray ab sorptiometry. in contrast, trabecular bone density determined from qua ntitative computed tomography was a poor predictor of compressive stre ngth, as was bone mineral content. Use of an integral measure of bone density may provide a more practical guide to bone fragility.